A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and so on.
Communication systems providing wireless communication for user equipment are known. Cellular communication systems are configured to have a cell structure, and typically they support communication with user equipment changing locations (mobile users). The support for communications for mobile users may include support for handing existing connections from one cell to another cell. At least routing of calls or communications for a mobile user in a new cell is typically supported in cellular systems. Some examples of a cellular system are the Global System for Mobile Telecommunications (GSM) and UMTS (Universal Mobile Telecommunication System).
A communication system may be circuit switched or packet switched. General Packet Radio Service (GPRS) provides packet-switched data services for the GSM and UMTS system.
A technical problem commonly encountered in telecommunications systems is how to reduce or minimize both power consumption of terminals and unnecessary signaling in the network. The issues of power consumption and unnecessary signaling are often linked due to the fact that signal transmission typically accounts for a major part of the overall power consumption of a terminal.
Reducing power consumption by terminals is particularly important in mobile telecommunications networks, due to the fact that mobile terminals are typically battery powered and thus have a finite power reserve. Excessive power consumption by mobile terminals can lead to unacceptably short intervals before the terminal battery needs to be recharged.
Power consumption of mobile terminals can be a particular problem when the terminal is running one or more “always-on” applications. Always-on applications require the terminal to be constantly attached to a radio network and to be reachable over the current radio technology. Examples of always-on applications include push e-mail, instant messaging, and voice and video telephony.
Many always-on applications need to transmit or receive frequent “keep-alive” messages during the idle times in order to refresh the soft state in the application servers or intermediate firewalls and Network Address Translation (NAT) devices. The keep-alive procedures may maintain the MS in states which consume so much energy that the battery lifetime will no longer be acceptable. Since IPsec Virtual Private Network (VPN) and Mobile IP sessions may be used with always-on applications to provide security and mobility, increasing the power efficiency of these protocols is particularly important.
Embodiments of the present invention aim to address one or more of the above-mentioned problems. In particular, embodiments of the present invention aim to reduce power consumption and/or unnecessary signalling by terminals in a communications network.